CSS - page-break-before

page-break-before 属性指示在元素框之前是否（以及有多少）允许分页符。

此属性的值并非决定是否应在元素后进行分页符的唯一因素。此决定还将受到前面元素的 page-break-after 值以及任何祖先元素的 page-break-inside 值的影响。

可能的值

auto − 在元素框之前不强制也不阻止分页符。
always − 在此元素框之前强制分页符。
avoid − 尽可能不在元素框之前放置分页符。
left − 在元素框之前强制一页或两页分页符，以便打印元素的下一页为左页。
right − 在元素框之前强制一页或两页分页符，以便打印元素的下一页为右页。

应用于

所有块级元素。

示例

这是一个示例：

<html>
   <head> 
   
      <style type = "text/css">
         p{page-break-before: always;}
      </style>
   </head>

   <body>
   
      <p>
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         Android offers a unified approach to application development for mobile devices which means developers need only develop for Android, and their applications should be able to run on different devices powered by Android.
         The first beta version of the Android Software Development Kit (SDK) was released by Google in 2007 where as the first commercial version, Android 1.0, was released in September 2008.
         On June 27, 2012, at the Google I/O conference, Google announced the next Android version, 4.1 Jelly Bean. Jelly Bean is an incremental update, with the primary aim of improving the user interface, both in terms of functionality and performance.
         The source code for Android is available under free and open source software licenses. Google publishes most of the code under the Apache License version 2.0 and the rest, Linux kernel changes, under the GNU General Public License version 2
      </p>
      
      <p>
         Android applications are usually developed in the Java language using the Android Software Development Kit.
         Once developed, Android applications can be packaged easily and sold out either through a store such as Google Play or the Amazon Appstore.
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      </p>
      
      <button onclick = "myFunction()">Print this page</button>
      
      <script>
         function myFunction() {
            window.print();
         }
      </script>
      
   </body>
</html>

打印页面